Pilot assisted modulation is commonly used for communication systems. In particular, a pilot per sub-channel is broadcast, providing channel estimation to aid in subsequent demodulation of a transmitted signal. Several pilot assisted modulation schemes are utilized by communication systems, and typically comprise broadcasting a known sequence at known time intervals. A receiver, knowing the sequence and time interval, utilizes this information in demodulating/decoding subsequent non-pilot broadcasts.
While the broadcasting of a known pilot sequence aids in coherent demodulation, a drawback exists in that in next-generation communication systems pilot overhead can reduce data throughput. For example, approximately 20–25% of an Orthogonal Frequency Division Multiplexing (OFDM) link (e.g., one pilot per four data baud, plus one trailing pilot baud) is spent on overhead for the pilots used for channel estimation and coherent demodulation. Therefore, a need exists for a method and apparatus for performing coherent demodulation that reduces the amount of pilot data broadcast to receiving units.